The present invention relates to silicon carbide and other films, and, more particularly, to controlled deposition of these films on a substrate.
Semiconductor, micro- and nanoelectromechanical systems (MEMS/NEMS) apply integrated circuit fabrication technology to fabricate optical, mechanical, electrochemical, and biosensor devices. One of the important steps in creating MEMS and NEMS devices is the deposition of thin films of material onto substrates. Once the films are deposited, various etching techniques may be employed to shape the deposited film.
In typical MEMS/NEMS devices, silicon is a primary material. Silicon carbide is a material that has very good physical and chemical characteristics, and is noted for these properties at temperatures above about 300° C. Silicon carbide is an advantageous material for use in films for MEMS and NEMS, particularly because of its exceptional electrical, mechanical, and chemical properties compared to silicon in normal and harsh operating environments.
One of the barriers limiting development of silicon carbide in MEMS production has been the inability to deposit uniform films of silicon carbide on large area substrates having properties that are advantageous to and required for MEMS and NEMS. Deposition of silicon carbide is conventionally subject to variations in residual stress, residual stress gradient, and electrical resistivity. These properties are important to the proper operation of MEMS and NEMS devices.
With silicon, residual stress, residual stress gradient and electrical resistivity can be controlled after the film is deposited by annealing the film at elevated temperatures. Annealing in silicon induces crystallographic changes that result in the modification of these properties. With single crystalline and polycrystalline silicon carbide, such an approach is not feasible because silicon carbide is chemically and crystallographically stable at conventional annealing temperatures. For silicon carbide films deposited on silicon substrates, annealing is completely ineffective because the non-silicon carbide substrate limits the annealing temperatures to temperatures too low for effective annealing. The present invention bypasses the need for annealing altogether by implementing control of the residual stress, residual stress gradient, and electrical resistivity in the silicon carbide films during the film formation (deposition) process.